I am a micrometeorologist with a research focus on the measurement and mathematical modeling of greenhouse gases exchange in the atmospheric boundary layer. I have worked for the eddy flux community (Ameriflux) for near ten years. My recent research has focused on canopy fluid mechanics by developing theory, designing observations and performing numerical simulations to help understand the physical, biological and chemical processes that control the exchange of trace gas between the vegetation and the atmosphere.
Several recent developments are useful in understanding fundamental problems of transport processes within canopy flows.
- The fundamental profiles (the S-shaped wind profile and exponential Reynolds profile) within canopy derived from the canopy momentum transfer (CMT) theory (Yi, 2008) are governed by vegetation structures and topography (Yi et al., 2005). These analytical models can be used as tools in the design and evaluation of the land-surface parameterizations for meso-scale models.
- A super-stable layer is founded to locate at about maximum drag elements level of a canopy, especially at calm night conditions (Yi et al, 2005; Yi, 2008). Canopy-flow properties of transport and mixing are different and uncorrelated between above and below the super-stable layer. The topographic advection error associated with eddy flux measurements are directly related to the occurrence of the super-stable layer (Yi et al., 2008). The super-stable layer theory is extremely useful in the experimental design for flux measurements and in data analysis. For example, the famous Keeling plot is gone in calm night as all data from canopy layer are used; however, the Keeling plot is recovered as the data are divided into two groups that are above/below the super-stable layer.
- The civic engineering CFD model is adopted to simulate canopy turbulent flow within and above canopy over complex terrain (Yi et al., 2005). This adapted numerical model can be used to study patchy-canopy processes in high resolution and how the patchy canopy processes significantly contribute to mesoscale processes.
- measuring and modeling turbulent transport processes over complex terrain
- studying instability of canopy flows over complex terrain
- measuring and modeling feedbacks between air quality and weather for a super-city
- upscaling the U.S. CO2 flux from tower sensors to satellite sensors
- improving the land surface parameterization of mesoscale models.
I believe that teaching undergraduates is quite different from teaching graduate students. A scientist’s foundation in science is built in undergraduate education and a person’s thinking habit is influenced by undergraduate education too. In contrast, graduate education places emphasis on training the research ability for the future scientists. Some further courses to learn for graduates are necessary to bring students from the classic ground to the research forefront. However, involving graduates in research associated with advisor’s projects are very important. I believe the most important ability for a graduate student is to identify an important scientific problem in their field and be able to concisely state it out. My philosophy is that when you clearly know what the scientific question is, you already know half of the answer to the question. The main goal of graduate education is not to learn more knowledge but to learn how to find a scientific problem and be able to solve the problem. When you need extra knowledge or skill to solve the problem, it is always possible to pick up the specific knowledge later.
- GEOL 216 Dynamics of the Ocean and Atmosphere
- ENSCI 100: Our Planet in the 21rst Century: Challenges to Humanity: Introduction to the Environment
- GEOL 011 Survey of Atmospheric Science
- GEOL 383 Topic: Meteorology
- ENSCI 112 Our Changing Planet
- ENSCI 111 Introduction to Environmental Science
- GEOL 520 Meteorology
- GEOL 799.3 Extreme Weather and Megacities
- GEOL 799.3 Atmosphere-Biosphere modeling
Yi, C., Instability analysis of terrain-induced canopy flows, Journal of the Atmospheric Sciences, 66, 2134-2142, doi:10.1175/2009JAS3005.1, 2009.
Yi, C., Momentum transfer within canopies, Journal of Applied Meteorology and Climatology, 47, 262-275, doi:10.1175/2007JAMC1667.1, 2008
Yi, C., D. E. Anderson, A. A. Turnipseed, S. P. Burns, and J. Sparks, D. Stannard, and K. R. Monson, The contribution of advective fluxes to net ecosystem CO2 exchange in a high-elevation, subalpine forest ecosystem, Invited Feature in Ecological Applications, 18 (6), 1379-1390, 2008.
Yi, C., R. K. Monson, Z. Zhai, D. E. Anderson, B. Lamb, G. Allwine, A. A. Turnipseed, and S. P. Burns, Modeling and measuring the nocturnal drainage flow in a high-elevation, subalpine forest with complex terrain, Journal of Geographical Research, 110, D22303, doi:10.1029/2005JD006282, 2005.
Yi, C., K. J. Davis, P. S. Bakwin, A.S. Denning, N. Zhang, A. Desai, J. C. Lin, and C. Gerbig, The observed covariance between ecosystem carbon exchange and atmospheric boundary layer dynamics at a site in northern Wisconsin, Journal of Geophysical Research, 109, D08302, doi:10.1029/2003JD004164, 2004a.
Yi, C., R. Li, P. S. Bakwin, A. Desai, D. M. Ricciuto, S. P. Burns, A. A. Turnipseed, S. C. Wofsy, J. W. Munger, K. Wilson, and R. K. Monson, A nonparametric method for separating photosynthesis and respiration components in CO2 flux measurements, Geophysical Research Letters, 31, L17107, doi:10.1029/2004GL020490, 2004b.
Yi, C., P. Gong, M. Xu , and Y. Qi , The effects of buffer and temperature feedback on the oceanic uptake of CO2, Geophysical Research Letter, 28, 751-754, 2001a.
Yi, C., K. J. Davis, P. S. Bakwin, B. W. Berger, Long-term observations of the dynamics of the continental planetary boundary layer, Journal of the Atmospheric Science, 58, 1288-1299, 2001b.
Yi, C., K. J. Davis, P. S. Bakwin, B. W. Berger, and L. Marr, The influence of advection on measurements of the net ecosystem-atmosphere exchange of CO2 from a very tall tower, Journal of Geophysical Research, 105, 9991-9999, 2000.
Yi, C., Nonlinear Sciences and Their Applications to the Geosciences, Meteorological Press, Beijing, 1995. (In Chinese)